1. Field of the Invention
The invention relates to a novel process for treating a composition comprising a trimethylolalkane bis-monolinear formal such as that obtained as a heavy ends residue from the purification of a crude trimethylolalkane product, to obtain useful compounds.
2. Description of the Related Art
Trimethylolpropane (TMP) and trimethylolethane (TME) are well-known chemical commodities used as intermediates in the production of a wide variety of products, e.g., varnishes, alkyd and polyester resins, synthetic drying oils, urethane foams and coatings, silicone lube oils, lactone plasticizers, textile finishes, surfactants, epoxidation products, etc. TMP and TME are made by reacting one mole of n-butyraldehyde or propionaldehyde respectively with an amount in excess of 3 moles of formaldehyde in an aqueous medium and in the presence of an alkaline condensation agent. However, these conditions result in the formation of not only TMP or TME, but also various higher boiling impurities. Thus it is necessary to subject the crude TMP or TME product obtained from the reaction to a purification process including distillation and solvent extraction steps, not only to separate relatively pure UMP or TME from excess formaldehyde, water, and basic condensation agent, but also from the higher boiling impurities.
A critical step in the purification process for obtaining relatively pure TMP or TME from the crude product of the reaction is a vacuum distillation or "flashing" of the bulk of the TMP or TME produced in the reaction, which is thus removed as a vapor from the higher boiling impurities remaining behind as a liquid heavy ends residue. While the residue may still contain some TMP or TME, the percentage of such desirable compound is fairly low and is difficult to recover economically. Furthermore, several of the high boiling impurities produced by the reaction in fairly large amounts have only limited commercial value. Thus, any expedient for treating the heavy ends residue, or any compound present in such residue in large amount, so as to convert at least a portion of such compound to TMP or TME and/or other more valuable compounds, would be very desirable.
U.S. Pat. No. 3,076,854 issued Feb. 5, 1963 to Klein, discloses the purification of crude TMP product by a process comprising extracting the reaction liquor with a water immiscible solvent for TMP, e.g., n-butanol or amyl alcohol, subjecting the extract to further extraction with water to obtain a re-extract containing TMP contaminated with metal formate and polyhydric by-products; separating the aqueous re-extract from the stripped solvent, heating the contaminated TMP with methanol or other lower alkanol and a mineral acid to convert the metal formate to a salt of the added acid, and further treating the aqueous TMP re-extract with an acidic cation-exchange resin to remove metal ions from the solution. British Patent No 1,290,036 discloses a process for removing trimethylpropane monomethyl formal from a crude TMP product by treating the product with a sulfonic acid cation exchange resin. The trimethylolpropane monomethyl formal decomposes to form trimethylolpropane monocyclic formal and methanol.
German Democratic Republic Patent No. 142184 discloses a process for the recovery of TMP from higher boiling residues comprising adding water and methanol to the residues such that they contain at least 15 wt. % of water or 10-40 wt. % of methanol, pretreating the residues with a cation exchange resin to remove traces of condensation agent contained in the residues, treating the residues under distillation conditions with a highly acidic, highly crosslinked cation-exchange resin with a polystyrene base, and recovering the TMP formed by conventional separation means.